Process for the preparation of a highly linear alcohol composition

ABSTRACT

Process for the preparation of a highly linear alcohol composition is provided comprising the steps of:  
     (a) reacting carbon monoxide with hydrogen under Fischer-Tropsch reaction conditions in the presence of a Fischer-Tropsch catalyst comprising cobalt;  
     (b) separating from the product of step (a) at least one hydrocarbon fraction comprising between 10 and 50% by weight of olefins containing 6 or more carbon atoms;  
     (c) contacting one or more of the hydrocarbon fractions obtained in step (b) with carbon monoxide and hydrogen under hydroformylation conditions in the presence of a hydroformylation catalyst based on a source of cobalt and one or more alkyl phosphines; and  
     (d) recovering the alcohol composition.

[0001] The present invention relates to a process for the preparation ofan alcohol composition, more specifically to a process for preparing analcohol composition having a high linearity.

[0002] It is known that oxo-alcohols can be prepared by hydroformylatingan olefin into an oxo-aldehyde followed by hydrogenation of thisoxo-aldehyde into the oxo-alcohol. Hydroformylation is typicallyconducted in the presence of a homogeneous catalyst which is based on asource of a transition metal, typically a metal of Group 8 (iron,ruthenium or osmium), 9 (cobalt, rhodium or iridium) or 10 (nickel,palladium or platinum) of the Periodic Table of Elements. In theircatalytically active form these metals may be used with carbonylligands, but they can also be used as a complex with other ligands,suitably phosphorus-containing ligands. Such catalysts are commonlyreferred to as phosphine and/or phosphite-modified hydroformylationcatalysts.

[0003] The secondary reaction, i.e. the hydrogenation of theoxo-aldehyde into the corresponding oxo-alcohol, occurs simultaneouslywith the actual hydroformylation reaction. Some of the homogeneoushydroformylation catalysts are sufficiently active to hydrogenate thein-situ formed oxo-aldehyde into the desired oxo-alcohol. Sometimes,however, a separate hydrofinishing step is applied in order to improvethe quality of the final oxo-alcohol product in terms of its aldehydecontent.

[0004] Oxo-alcohols may be very useful as plasticizers or detergents.Typically, plasticizer alcohols comprise from 7 to 11 carbon atoms,while detergent alcohols comprise from 12 to 15 carbon atoms. Animportant element determining the plasticizer and detergent propertiesof the final oxo-alcohol product is the linearity of the product.Throughout this specification the linearity of an alcohol product isdefined as the weight percentage of linear primary mono-alcoholsrelative to the total amount of alcohols. In general, conventionaloxo-processes typically produce alcohols having a linearity of 50 to 60%by weight.

[0005] The quality of the olefin feed to the hydroformylation is animportant factor in relation to the final properties of the alcoholproduct. In particular the amount of linear mono-olefins relative to thetotal amount of olefins present in the feed is an important factor.

[0006] In one aspect the present invention aims to provide an optimumquality olefin feed.

[0007] International Application No. WO 97/01521 discloses a process forproducing oxygenated products, typically aldehydes and alcohols, from anolefin-rich feedstock, which process comprises reacting, in ahydroformylation stage, a Fischer-Tropsch derived olefinic product withcarbon monoxide and hydrogen in the presence of a catalyticallyeffective quantity of a hydroformylation catalyst and underhydroformylation reaction conditions, to produce oxygenated productscomprising aldehydes and/or alcohols. The olefin-rich feedstocktypically contains from 35 to 100% by weight olefins, of which olefins50 to 100% by weight are linear α-olefins, 0 to 60% by weightmono-methyl branched α-olefins and 0 to 10% by weight linear internalolefins. The minimum olefin content of the feeds used in the workingexamples is 50% by weight (Examples 9 and 10). The Fischer-Tropschderived olefinic product is the product obtained by subjecting asynthesis gas comprising carbon monoxide and hydrogen to Fischer-Tropschreaction conditions in the presence of an iron-based, a cobalt-based oran iron/cobalt-based Fischer-Tropsch catalyst. A clear preference isexpressed for iron-based Fischer-Tropsch catalysts, which is alsoillustrated by the fact that in all working examples describinghydroformylation experiments the hydroformylation feed was based on theproduct of a Fischer-Tropsch reaction wherein a fused iron catalyst wasused.

[0008] In the process according to International Application No. WO97/01521 the feedstock to the hydroformylation reaction stage is anolefin-rich feedstock, which is obtained by reacting carbon monoxide andhydrogen in a Fischer-Tropsch reaction followed by subjecting theFischer-Tropsch reaction product to distillation treatments. Suchdistillation treatments are required in order to obtain the carbonfractions with the prescribed minimum olefin content of 35% by weight.

[0009] However, the process according to WO-A-97/01521 leaves room forimprovement in terms of the combination of alcohol selectivity in thehydroformylation and linearity of the alcohols produced. This is firstof all illustrated by the working examples of WO-A-97/01521: in all butone examples where a Fischer-Tropsch feed is used the linearity is atthe typical level, while alcohol selectivity is not optimal. In the onlyexample reporting a very high linearity of 84% (Example 5) the alcoholselectivity is only 64%, implying that relatively many by-products areformed. The olefin conversion in this example is also relatively poor:only 68%. Secondly, it was found that when using a fused iron catalystthe resulting olefin stream is characterised by a relatively highcontent of branched olefins. This is not beneficial for a high linearityof the alcohol product in combination with a high alcohol selectivity.Finally, the high olefin content of the hydroformylation feed, aprerequisite according to WO-A-97/01521, implies that quite a severedistillation treatment of the Fischer-Tropsch reaction product isrequired.

[0010] The present invention aims to overcome these shortcomings. Morespecifically, the present invention aims to provide a process forproducing oxo-alcohols by the hydroformylation of Fischer-Tropschproduct streams, which results in highly linear alcohols in combinationwith a high alcohol selectivity in the hydroformylation stage, thuslimiting the amount of by-products formed. The expression “selectivity”as used throughout this specification refers to the percentage ofalcohol products formed relative to the amount of total products formedfrom the converted olefins:

selectivity=amount alcohols formed×100%/total amount reaction products

[0011] Furthermore, in the process of the present invention very higholefin conversion rates should be attainable, while it should also notbe required to use hydroformylation feeds comprising 35% by weight ormore of olefins.

[0012] It was surprisingly found that by selecting specific types ofcatalysts in both the Fischer-Tropsch and hydroformylation stage highlylinear alcohol products could be obtained at very high alcoholselectivity and conversion rates.

[0013] The present invention provides a process for the preparation ofan alcohol composition comprising one or more primary mono-alcohols, atleast 60% by weight of which consists of linear primary mono-alcoholscontaining at least 7 carbon atoms. The process contains the steps of:

[0014] (a) reacting carbon monoxide with hydrogen under Fischer-Tropschreaction conditions in the presence of a Fischer-Tropsch catalystcomprising cobalt;

[0015] (b) separating from the product of step (a) at least onehydrocarbon fraction comprising between 10 and 50% by weight of olefinscontaining 6 or more carbon atoms;

[0016] (c) contacting one or more, of the hydrocarbon fractions obtainedin step (b) with carbon monoxide and hydrogen under hydroformylationconditions in the presence of a hydroformylation catalyst based on asource of cobalt and one or more alkyl phosphines; and

[0017] (d) recovering the alcohol composition.

[0018] Accordingly, a process for the preparation of an alcoholcomposition is provided, comprising at least one primary mono-alcohol,at least 60% by weight of which consists of linear primary mono-alcoholscontaining at least 7 carbon atoms, said process comprising the stepsof:

[0019] (a) reacting carbon monoxide with hydrogen under Fischer-Tropschreaction conditions in the presence of a Fischer-Tropsch catalystcomprising cobalt;

[0020] (b) separating from the product of step (a) at least onehydrocarbon fraction comprising between 10 and 50% by weight of olefinscontaining 6 or more carbon atoms;

[0021] (c) contacting at least one of the hydrocarbon fractions obtainedin step (b) with carbon monoxide and hydrogen under hydroformylationconditions in the presence of a hydroformylation catalyst based on asource of cobalt and one or more alkyl phosphines thereby producing ahydroformylation product stream; and

[0022] (d) recovering the alcohol composition from the hydroformylationproduct stream.

[0023] Alcohol composition comprising C12/C13 linear primarymono-alcohols and C12/C13 iso-alcohols, wherein the weight ratio C12linear primary alcohol to C13 linear primary alcohol is in the range offrom 0.5 to 2.0.

[0024] Alcohol composition comprising C14/C15 linear primarymono-alcohols and C14/C15 iso-alcohols, wherein the weight ratio C14linear primary alcohol to C15 linear primary alcohol is in the range offrom 1.0 to 3.0.

[0025] The alcohol composition finally obtained suitably comprises atleast 60% by weight, more suitably at least 65% by weight, of linear C7+primary mono-alcohols. Preferred compositions comprise at least 65% byweight of C10+ primary mono-alcohols. Typically, the maximum chainlength of linear primary mono-alcohols present in the alcoholcomposition will be 20 carbon atoms, more preferably 18 carbon atoms andeven more preferably 16 carbon atoms. The process of the presentinvention has been found particularly advantageous for preparingcompositions comprising one or more of C11, C12, C13 and C14 linearprimary mono-alcohols as the main component(s), while alcoholcompositions comprising as main components a combination of C12 and C13primary mono-alcohols or a combination of C14 and C15 primarymono-alcohols have been found particularly useful. However, also loweralcohol compositions may be prepared, notably compositions comprisingcombinations of C7, C8 and/or C9 primary mono-alcohols and compositionscomprising a combination of C9, C10 and/or C11 primary mono-alcohols.

[0026] In step (a) of the present process hydrocarbons are prepared byreacting carbon monoxide and hydrogen under conditions effective toproduce hydrocarbons. In general, the preparation of hydrocarbons from amixture of carbon monoxide and hydrogen at elevated temperature andpressure in the presence of a catalyst effective to produce hydrocarbonsis known as the Fischer-Tropsch hydrocarbon synthesis. Catalysts used inthis hydrocarbon synthesis are normally referred to as Fischer-Tropschcatalysts and usually comprise one or more metals from Groups 8, 9 and10 of the Periodic Table of Elements, optionally together with one ormore promoters, and a carrier material. In particular, iron, nickel,cobalt and ruthenium are known to be catalytically active metals forsuch catalyst. The Fischer-Tropsch catalyst to be used in step (a) ofthe present process, however, should comprise cobalt as thecatalytically active metal. The catalyst also comprises a porous carriermaterial, in particular a refractory oxide carrier. Suitable refractoryoxide carriers include, for example, alumina, silica, titania, zirconiaor mixtures thereof, such as silica-alumina or physical mixtures such assilica and titania. Very suitable carriers are those comprising titania,zirconia or mixtures thereof. Titania carriers are preferred, inparticular titania which has been prepared in the absence ofsulphur-containing compounds. This carrier may further comprise up to50% by weight of another refractory oxide, typically silica or alumina.More preferably, the additional refractory oxide, if present,constitutes up to 20% by weight, even more preferably up to 10% byweight, of the carrier.

[0027] Typically, the catalyst comprises 1-100 parts by weight of cobalt(calculated as element), preferably 3-60 parts by weight and morepreferably 5-40 parts by weight, per 100 parts by weight of carrier.These amounts of cobalt refer to the total amount of cobalt in elementalform and can be determined by known elemental analysis techniques.

[0028] In addition to cobalt the catalyst may comprise one or morepromoters. Suitable promoters include manganese, zirconium, titanium,ruthenium, platinum, vanadium, palladium and/or rhenium. The amount ofpromoter, if present, is typically between 0.1 and 150 parts by weight(calculated as element), for example between 0.25 and 50, more suitablybetween 0.5 and 20 and even more suitably between 0.5 and 10, parts byweight per 100 parts by weight of carrier.

[0029] Typically, the Fischer-Tropsch catalyst does not contain alkalior alkaline earth metals, apart from possible impurities introduced withstarting materials in the preparation process of the catalysts of thepresent invention. Typically, the atomic ratio of alkali or alkalineearth metals to cobalt metal is less than 0.01, preferably, less than0.005.

[0030] The Fischer-Tropsch process conditions applied in step (a) of thepresent process typically include a temperature in the range from about125 to about 350° C., preferably from about 160 to about 275° C., morepreferably from about 175 to about 250° C., even more preferably fromabout 190 to about 240° C., and especially from about 190 to about 235°C., and a pressure in the range from about 5 to about 150 bar abs. Step(a) of the present process may be operated at the pressuresconventionally applied, i.e. up to about 80 bar abs., suitably up to 65bar abs., but also higher pressures can be applied.

[0031] In a preferred embodiment of the present invention step (a)comprises reacting carbon monoxide with hydrogen at a temperature in therange of from about 125 to about 350° C. and a pressure in the rangefrom about 5 to about 150 bar in the presence of a catalyst comprisingcobalt on a carrier comprising titania. Suitably, the catalyst andprocess conditions in step (a) are selected such that the productobtained in this step (a) comprises in the range of from 2 to 20% byweight of a C11 to C14 hydrocarbon fraction, which hydrocarbon fractioncomprises in the range of from 10 to 50% by weight based on total weightof this fraction of C11 to C14 mono-olefins. This could, for instance,be achieved by using a Fischer-Tropsch catalyst based on cobalt andtitania at operating temperatures of about 175 to about 275° C. andoperating pressures of from about 30 up to about 65 bar abs.

[0032] In a further preferred embodiment of the present invention thepressure applied in step (a) is at least about 40 bar, preferably atleast 50 bar. A much preferred pressure range is about 50 to about 150bar, even more preferably from about 55 to about 140 bar. Operatingtemperatures at these pressures may be those normally applied, butpreferred operating temperatures at these pressures are in the range offrom about 150 to about 250° C., more preferably from about 160 to about230° C.

[0033] Hydrogen and carbon monoxide (synthesis gas) are typically fed tothe reactor at a molar ratio in the range from 0.5 to 4, preferably from0.5 to 3, more preferably from 0.5 to 2.5 and especially from 1.0 to1.5. These molar ratios are preferred for the case of a fixed bedreactor.

[0034] The Fischer-Tropsch reaction step (a) may be conducted using avariety of reactor types and reaction regimes, for example a fixed bedregime, a slurry phase regime or an ebullating bed regime. It will beappreciated that the size of the catalyst particles may vary dependingon the reaction regime they are intended for. It is within the normalskills of the skilled person to select the most appropriate catalystparticle size for a given reaction regime.

[0035] Further, it will be understood that the skilled person is capableto select the most appropriate conditions for a specific reactorconfiguration and reaction regime. For example, the preferred gas hourlyspace velocity may depend upon the type of reaction regime that is beingapplied. Thus, if it is desired to operate the hydrocarbon synthesisprocess with a fixed bed regime, preferably the gas hourly spacevelocity is chosen in the range from about 500 to about 2500 Nl/l/h. Ifit is desired to operate the hydrocarbon synthesis process with a slurryphase regime, preferably the gas hourly space velocity is chosen in therange from about 1500 to about 7500 Nl/l/h.

[0036] After carbon monoxide and hydrogen have reacted into ahydrocarbon product in step (a), in subsequent step (b) this hydrocarbonproduct is separated into one or more hydrocarbon fractions comprisingbetween 10 and 50% by weight, preferably between 15 and 45% by weight,of olefins containing 6 or more carbon atoms. Very good results havealso been achieved when separating the hydrocarbon in step (b) into atleast one hydrocarbon fraction containing less than 35% by weight ofolefins. It was found that such fraction, which has a relatively lowolefin content, is also a very good feedstock for the hydroformylationin step (c) and also results in alcohol products with high linearitiesand excellent alcohol selectivities. Preferably the separation in step(b) involves a distillation treatment, notably fractional distillation.Conventional distillation techniques can be used.

[0037] The separation in step (b) may be effected by fractionaldistillation, but could also comprise a combination of distillation withanother separation treatment, such as condensation and/or extraction.

[0038] In a preferred embodiment the hydrocarbon fractions recoveredafter fractional distillation in step (b) are the C8-C10, C11-C12 andC13-C14 fractions, each containing at most 5% by weight, but morepreferably at most 2% by weight, of the neighbouring hydrocarbonfractions. Also the C6-C8 fraction is a preferred fraction, containingat most 5% by weight, but more preferably at most 2% by weight, of theneighbouring C5 and C9 hydrocarbon fractions. Each hydrocarbon fractionof carbon number n (so n being an integer of from 6 to 14) suitablycontains 10 to 50% by weight, more suitably 20 to 45% by weight, ofCn-olefins. However, as already indicated hereinbefore, hydrocarbonfractions containing less than 35% by weight of olefins are also veryuseful. These hydrocarbon fractions can be used individually as feed tohydroformylation step (c), but two or more of these fractions may alsobe combined into a feed stream to the hydroformylation in step (c). Theprocess of the present invention is particularly suitable when usingC11-C12 hydrocarbon streams and C13-C14 hydrocarbon streams as feed instep (c).

[0039] In step (c) hydroformylation takes place. For the purpose of thepresent invention it was found very advantageous to use as a feed instep (c):

[0040] (1) a hydrocarbon stream comprising at least 30% by weight of C11and C12 n-alkanes and from 15 to 50% by weight of linear C11 and C12mono-olefins (i.e. including 1-olefins, 2-olefins and internal olefins),or

[0041] (2) a hydrocarbon stream comprising at least 30% by weight of C13and C14 n-alkanes and from 10 to 45% by weight of linear C13 and C14mono-olefins.

[0042] The feed described above under (1) suitably comprises from 55 to75% by weight of n-alkanes and from 20 to 45% by weight of linear C11and C12 mono-olefins, at least 75% by weight and preferably at least 80%by weight of which consists of linear C11 and C12 mono-α-olefins. Inaddition to the n-alkanes and mono-olefins the feed may also containrelatively small amounts of other components (typically up to a total of15% by weight, preferably less than 10% by weight and more preferablyless than 7% by weight), such as alcohols, C10 and C13 n-alkanes, C13+olefins, branched olefins and branched alkanes.

[0043] The feed described above under (2) suitably comprises from 60 to80% by weight of n-alkanes and from 15 to 40% by weight of linear C13and C14 mono-olefins, at least 70% by weight and preferably at least 80%by weight of which consists of linear C13 and C14 mono-α-olefins. Inaddition to the n-alkanes and mono-olefins the feed may also containsmall amounts of other components (typically up to a total of 15% byweight, preferably less than 10% by weight and more preferably less than8% by weight), such as alcohols, C12 and C15 n-alkanes, C15+ olefins,branched olefins and branched alkanes.

[0044] The hydroformylation catalyst used in step (c) is based on asource of cobalt and one or more alkyl phosphines, more in particularphosphorus-containing ligand modified cobalt-based catalysts. Suchcatalysts are known in the art and are, for instance described in U.S.Pat. Nos. 3,239,569; 3,239,571; 3,400,163; 3,420,898; 3,440,291 and3,501,515, which are incorporated by reference herein. For the purposeof the present invention it has, however, been found particularlyadvantageous to use homogeneous hydroformylation catalysts comprisingcobalt as the catalytically active metal in combination with eithertrialkyl phosphines or optionally substituted monophosphabicycloalkanesas the ligands. Particularly the substituted or unsubstitutedmonophosphabicycloalkanes are preferred. Accordingly, the most preferredcatalysts are those based on a source of cobalt and amonophosphabicycloalkane-ligand, wherein the phosphorus atom issubstituted with hydrogen or non-acetylenic hydrocarbyl of 1 to 36carbon atoms (e.g. alkyl or aryl) and this phosphorus atom is a memberof a bridge linkage without being a bridgehead atom and whichmonophosphabicylcoalkane has 7 to 46 carbon atoms, 7 or 8 carbon atomsof which together with the phosphorus atom being members of the bicyclicskeletal structure. Preferred monophosphabicycloalkane ligands comprise(i) an alkyl substituent of 4 to 30, more preferably 5 to 25, carbonatoms, or a phenyl substituent or hydrogen with (ii) 8 carbon atomstogether with the phosphorus-atom forming the bicyclic skeletalstructure. Particularly preferred ligands are9-eicosyl-9-phosphabicyclo[4.2.1]nonane;9-eicosyl-9-phosphabicyclo[3.3.1]nonane; 9-phenyl-9-phosphabicyclo[4.2.1]nonane and 9-phosphabicyclo[4.2.1]nonane. These ligands as wellas their preparation are disclosed in U.S. Pat. No. 3,400,163, whiletheir use in hydroformylation reactions is disclosed in U.S. Pat. No.3,420,898, both incorporated by reference herein.

[0045] The alkyl phosphine is used in such amount that the molar ratioof alkyl phosphine to cobalt is in the range of from 0.5 to 2,preferably 0.6 to 1.8. In addition to the cobalt and the alkylphosphine, the hydroformylation catalyst may also comprise additionalcomponents for enhancing the stability of the Co/phosphine system and/orfor improving the alcohol selectivity. Suitable additional componentsinclude strong bases, such as KOH and NaOH with KOH being particularlypreferred. The additional component is typically used in such amountthat the molar ratio of this component to cobalt is in the range of from0 to 1.

[0046] The hydroformylation reaction in step (c) can be carried outunder conventional hydroformylation conditions. Accordingly, suitableconditions include reaction temperatures in the range of from about 100to about 300° C., preferably from about 125 to about 250° C., andpressures from about 1 to about 300 bar, preferably from about 20 toabout 150 bar. The amount of catalyst relative to the amount of olefinto be hydroformylated is not critical and may vary widely. Typical molarratios of catalyst to olefin in the reaction mixture at any given momentduring the reaction may be in the range of from 1:1000 to 10:1. A ratioof between 1:10 and 5:1 is often used. The hydroformylation may involvethe use of a solvent that does not interfere substantially with thedesired reaction. Such solvents include saturated liquid organicsolvents like alcohols, ethers, acetonitrile, sulfolane, paraffins andmany more. It is, however, preferred not to use an additional solvent,but to use the reactant stream itself as the liquid reaction medium.

[0047] The ratio of carbon monoxide to hydrogen applied in step (c) mayvary widely. It is, however, preferred that the hydrogen to carbonmonoxide molar ratio in step (c) is in the range of from 1.0 to 5.0,more preferably from 1.5 to 2.5.

[0048] Typically synthesis gas, i.e. a blend of carbon monoxide andhydrogen, is used, but in principle both gases may also be fedindependently from each other to the hydroformylation reaction medium.Preferably, however, synthesis gas or syngas is used. Syngas istypically made by partial combustion of a petroleum feed and commercialsyngas normally comprises hydrogen (H₂) and carbon monoxide (CO) in aH₂/CO molar ratio of from 1 to 2.5. Higher molar ratios up to 10.0 couldalso occur in syngas, e.g. syngas prepared by the watergas shiftreaction, and such syngas could also be used. Accordingly, suitablesyngas comprises hydrogen and carbon monoxide in a H₂/CO molar ratio offrom about 1.0 to about 10.0, preferably from 1.0 to 5.0. A molar ratiobetween 1.5 and 2.5 is most preferred.

[0049] The hydroformylation step (c) may be carried out in a continuous,semi-continuous or batch mode. In case of a continuous mode ofoperation, the liquid hourly space velocities typically are in the rangeof from about 0.1 to about 10 h⁻¹. When operating step (c) as a batchprocess, reaction times may suitably vary from about 0.1 to about 10hours or even longer.

[0050] By operating the hydroformylation step (c) as describedhereinbefore alcohol selectivities of at least 90% and even of at least92% are achieved, while at the same time the linearity of the alcoholproduct obtained is at least 70% by weight, suitably at least 75% byweight, for the C7-C13 mono-alcohols and at least 60% by weight,suitably at least 65% by weight for the C14-C15 alcohols. In addition,olefin conversions as high as 95% by weight or more and even 99% byweight or more are achieved.

[0051] Step (d) of the present process involves recovering of the linearmono-alcohol product from the hydroformylation reaction product. Thiscan be achieved by methods known in the art.

[0052] In a preferred embodiment step (d) comprises the steps of a firstdistillative treatment, saponification, water washing treatment and asecond distillative treatment. Accordingly, in this mode of operationthe hydroformylation reaction product of step (c) is first subjected toa first distillative treatment, after which the alcoholproduct-containing fraction obtained is subjected to a saponificationtreatment to remove any acids and esters followed by a water washingtreatment to remove the sodium salts. The water-washed product is thensubjected to a second distillative treatment to remove any remainingimpurities or by-products.

[0053] The first distillative treatment preferably is a treatmentresulting in a top fraction containing most (i.e. more than 50% byweight, preferably at least 70% weight, more preferably at least 80% byweight) of the alcohol product formed and a bottom fraction containingheavier components together with the rest of the alcohol product formed.The bottom fraction is suitably recycled, at least partly, and againsubjected to the distillative treatment. Examples of suitabledistillative treatments include flashing and short path distillation,the latter treatment being particularly preferred for the purpose of thepresent invention. However, other distillative treatments may also beused.

[0054] The (top) fraction containing most of the alcohol productobtained from the distillative treatment is subsequently subjected to asaponification treatment in order to remove any acids and esters, mostlyformate esters, present. Saponification is typically carried out bycontacting the alcohol-containing fraction with an aqueous solution of astrong basic hydroxide, typically sodium hydroxide (NaOH) or sodiumboron hydride (NaBH₄), at elevated temperature and whilst stirring. Forexample, saponification may be carried out by contacting the alcoholfraction with an aqueous 0.5 to 10%, suitably 1 to 5%, NaOH solution atan organic/water phase ratio of 10:1 to 1:1, suitably 8:1 to 2:1, theexact ratio depending on the estimated amount of esters and acidspresent. Saponification can be carried out batch-wise or continuously,whereby each alcohol fraction is normally one to three times subjectedto saponification. Typical saponification temperatures are in the rangeof from about 40 to about 99° C., suitably from about 60 to about 95° C.Due to the stirring conditions an emulsion in normally formed, thusallowing the saponification reactions to take place. When stirring isstopped, phase separation occurs and the organic phase containing 90% byweight or more of the alcohol product is recovered for furthertreatment.

[0055] The organic phase recovered from the saponification is subjectedto a water wash treatment to remove the sodium salts present. Typicallysuch water washing treatment involves from one to five water washes. Awater wash is typically carried out by mixing the saponification productwith water and subsequently allowing phase separation to occur. Thesodium salts will then be contained in the water phase. The water phaseand organic (alcohol-containing) phase are then separated. Details ofsuitable water wash treatments are well known to those skilled in theart.

[0056] To further increase the purity of the alcohol product obtainedthe water washed alcohol product is subjected to a further distillativetreatment to remove any components which are lighter and/or heavier thanthe desired alcohol products. Such “topping and tailing” treatment canbe carried out using conventional distillation techniques. For instance,fractional distillation can be used, thereby collecting those fractionswhich meet the specifications set and possibly combining them into oneor more crude alcohol fractions.

[0057] The crude alcohol product obtained may still contain residualaldehydes and hemi-acetals. Such components could be adequately removedby subjecting the alcohol product from the topping and tailing treatmentto a hydrofinishing treatment. This is a hydrogenation reaction carriedout under relatively mild conditions. It can be carried out byconventional hydrogenation processes, such as by passing the crudealcohol feed together with a flow of hydrogen over a bed of a suitablehydrogenation catalyst. Such catalysts are well known in the art andtypically comprise a metal with hydrogenation functionality, such asnickel, palladium or platinum, on a refractory oxide support such asalumina, silica or silica-alumina. The hydrogenation temperature andhydrogen pressure may vary within wide limits and typically rangerespectively from about 50 to about 250° C., preferably about 100 toabout 200° C., and from about 10 to about 150 bar abs., preferably about20 to about 100 bar abs. The hydrofinished alcohol product obtained fromthe hydrofinishing is the final alcohol product.

[0058] In a further aspect the present invention also relates to analcohol composition comprising

[0059] (a) 70 to 90% by weight, preferably 75 to 85% by weight, of C12and C13 linear primary mono-alcohols

[0060] (b) 10 to 30% by weight, preferably 15 to 25% by weight, of C12and C13 iso-alcohols

[0061] wherein the weight ratio C12 linear primary alcohol to C13 linearprimary alcohol is in the range of from 0.5 to 2.0.

[0062] The expression “iso-alcohols” as used in this connection refersto the 2-methyl isomers of the primary mono-alcohols mentioned under(a).

[0063] In a final aspect the present invention also relates to analcohol composition comprising

[0064] (a) 55 to 80% by weight, preferably 60 to 75% by weight, of C14and C15 linear primary mono-alcohols

[0065] (b) 20 to 45% by weight, preferably 25 to 40% by weight, of C14and C15 iso-alcohols

[0066] wherein the weight ratio C14 linear primary alcohol to C15 linearprimary alcohol is in the range of from 1.0 to 3.0.

[0067] The above alcohol compositions can be obtained by the processdescribed hereinbefore.

[0068] The invention will now be illustrated by the following exampleswithout limiting the scope of the invention to these particularembodiments.

EXAMPLE 1

[0069] In a Fischer-Tropsch reaction stage synthesis gas containinghydrogen and carbon monoxide in a molar ratio of about 2:1 was passedover a fixed bed of activated Fischer-Tropsch catalyst extrudates at apressure of 60 bar and a weighted average bed temperature (WABT) of 205°C. The Fischer-Tropsch catalyst was a CoMn/titania catalyst. The GHSVamounted to 800 Nl/l/h.

[0070] The reaction product was passed into a condenser operated at 60bar and 205° C. resulting in a heavy liquid product and a gaseousproduct comprising all reaction products having a boiling point below205° C. This gaseous stream was liquefied by cooling it to 15° C. andthe liquid stream obtained was subsequently subjected to a number ofbatch fractionation treatments using a 15 tray Fischer packeddistillation column. Firstly, the C6-C10 hydrocarbon fractions wereremoved and subsequently the C11/C12 and C13/C14 fractions wererecovered. The compositions of both these fractions are given inTable 1. TABLE 1 Hydroformylation feeds C11/C12 fraction C13/C14fraction C9 (% w) alcohol 2.0 C10 (% w) n-alkane 0.9 alcohol 2.0 C11 (%w) 1-olefin 13.4 2-olefin 2.9 internal olefin 0.2 n-alkane 32.3 alcohol2.3 C12 (% w) 1-olefin 11.9 2-olefin 2.2 internal olefin 0.5 n-alkane29.8 0.9 alcohol 1.9 C13 (% w) 1-olefin 10.4 2-olefin 3.1 internalolefin 0.6 n-alkane 0.7 36.6 C14 (% w) 1-olefin 8.1 2-olefin 2.1internal olefin 0.7 n-alkane 31.9 C15 (% w) 1-olefin 0.5 n-alkane 0.2Total olefin (% w) 31.1 25.7

EXAMPLE2

[0071] The C11/C12 fraction was subjected to a hydroformylationtreatment as follows.

[0072] A 1.5 litre autoclave was charged with 597.1 grams ofhydroformylation feed, 9.9 grams of n-C10 alkane (as internal standardfor subsequent GC analysis) and 7.3 grams of a 5.81% by weight KOHsolution in 2-ethylhexanol. The autoclave was pressurized to 30 bar withsynthesis gas (ratio H₂/CO=2) and heated to 185° C. Then 33.6 grams of acatalyst solution were injected. This catalyst solution was obtained bypremixing 214.8 grams of a 70% by weight cobalt octoate solution inShellsol 140T (a paraffinic solvent; Shellsol is a trade mark) with221.4 grams of 9-eicosyl-9-phosphabicyclononane ligand. Accordingly, theamount of cobalt was 0.285% by weight based on total weight of reactorcontents, the ligand/cobalt molar ratio was 1.2 and the K/Co molar ratiowas 0.2. Immediately after injection of the catalyst solution thepressure in the autoclave was increased to 70 bar with synthesis gas(ratio H₂/CO=2).

[0073] After two hours the conversion of olefins was complete. Duringthese two hours the reaction temperature rose to 196° C. The compositionof the crude C12/C13 alcohol product is indicated in Table 2.

EXAMPLE 3

[0074] Example 2 was repeated except that the C13/C14 fraction was nowtaken as the hydroformylation feed. The amounts of the variouscomponents used were 546 grams of C13/C14 fraction, 9.1 grams of n-C10alkane, 6.7 grams of the 5.81% by weight KOH solution in 2-ethylhexanoland 31.0 grams of the catalyst solution.

[0075] After two hours the conversion of olefins was complete. Duringthese two hours the reaction temperature rose to 195° C. The compositionof the crude C14/C15 alcohol product is also indicated in Table 2. TABLE2 Crude alcohol products C12/C13 alcohol C14/C15 alcohol n-alkanes (% w)59.1 68.1 aldehydes (% w) 0.1 0.1 alcohols (% w) n-C9-OH 2.1 n-C10-OH2.0 n-C11-OH 2.1 n-C12-OH/i-C12-OH* 12.9/3.7 1.8/0.0 n-C13-OH/i-C13-OH10.9/3.3 n-C14-OH/i-C14-OH  0.5/0.1 8.4/4.6 n-C15-OH/i-C15-OH 5.9/3.1n-C16-OH 0.1 other (% w)** 5.3 5.8 linearity (% w) 77 65 alcoholselectivity (%) 94 94 Conversion (% w) 99.8 99.8

EXAMPLE 4

[0076] The crude alcohol products of examples 2 and 3 were worked up bythe subsequent steps of wiped film evaporation, saponification of thetop fractions, batch distillation treatment to remove the top and tailfractions and hydrofinishing.

[0077] Wiped film evaporation was carried out at a temperature of 110°C. (for the crude C12/C13 alcohol product) or 120° C. (for the C14/C15crude alcohol product), a 1 mbar abs. vacuum, a cold finger temperatureof 5° C., a stirrer speed of 375 rpm and a flow rate of 16 ml/min. Theobtained splits in top/bottom w/w ratios were 91/9 for the crude C12/C13alcohol product and 90/10 for the crude C14/C15 alcohol product.

[0078] The top fraction of the wiped film evaporation was saponified bycontacting it at 90° C. with an aqueous 3% NaOH solution at a phaseratio organic:water of 4:1 for the crude C12/C13 alcohol product andwith an aqueous 5% NaOH solution at a phase ratio organic:water of 6:1for the crude C14/C15 alcohol product. After phase separation theorganic phase was three times washed with water under similarconditions.

[0079] The saponified alcohol products were subsequently topped toremove the light by-products and tailed to remove the heavierby-products by distillative treatment using a 15 tray Fischer packeddistillation column. The resulting crude C12/C13 and C14/C15 alcoholproducts contained respectively 84% by weight and 89% by weight ofalcohol.

[0080] These crude alcohol products were then subjected to ahydrofinishing treatment by contacting the crude alcohol (at 0.8 ml/min)with hydrogen (at 5 l/h) in a trickle flow hydrogenation columncontaining 14 grams of a nickel/alumina hydrogenation catalyst (HTC 400ex Crossfield) at 120° C. and a constant hydrogen pressure of 60 bar.

[0081] The yield (relative to the C11/C12 respectively C13/C14 feed tothe hydroformylation reaction), composition and linearity of thefinished alcohol products obtained is given in Table 3. TABLE 3 Finishedalcohol products C12/C13 alcohol C14/C15 alcohol n-alkanes (% w) 0.2 0.0alcohols (% w) n-C10-OH 0.2 n-C11-OH 0.6 n-C12-OH/i-C12-OH 45.6/5.6 0.4/0.0 n-C13-OH/i-C13-OH 35.1/12.1 0.7/0.0 n-C14-OH/i-C14-OH 0.1/0.043.6/16.6 n-C15-OH/i-C15-OH 22.3/15.3 n-C16-OH 0.1 Linearity (% w) 81 66Yield (% w)* 57 60

We claim:
 1. A process for the preparation of an alcohol compositioncomprising at least one primary mono-alcohol, at least 60% by weight ofwhich consists of linear primary mono-alcohols containing at least 7carbon atoms, said process comprising the steps of: (a) reacting carbonmonoxide with hydrogen under Fischer-Tropsch reaction conditions in thepresence of a Fischer-Tropsch catalyst comprising cobalt; (b) separatingfrom the product of step (a) at least one hydrocarbon fractioncomprising between 10 and 50% by weight of olefins containing 6 or morecarbon atoms; (c) contacting at least one of the hydrocarbon fractionsobtained in step (b) with carbon monoxide and hydrogen underhydroformylation conditions in the presence of a hydroformylationcatalyst based on a source of cobalt and one or more alkyl phosphinesthereby producing a hydroformylation product stream; and (d) recoveringthe alcohol composition from the hydroformylation product stream.
 2. Theprocess of claim 1 wherein step (a) comprises reacting carbon monoxidewith hydrogen at a temperature in the range of from about 125 to about350° C. and a pressure in the range from about 5 to about 150 bar abs.in the presence of a Fischer-Tropsch catalyst comprising cobalt on acarrier comprising titania.
 3. The process of claim 1 wherein theseparation in step (b) involves a distillation treatment.
 4. The processof claim 1 wherein the hydrocarbon fraction in step (c) is a hydrocarbonstream comprising at least 30% by weight of C11 and C12 n-alkanes andfrom 15 to 50% by weight of linear C11 and C12 mono-olefins.
 5. Theprocess of claim 1 wherein the hydrocarbon fraction in step (c) is ahydrocarbon stream comprising at least 30% by weight of C13 and C14n-alkanes and from 10 to 45% by weight of linear C13 and C14mono-olefins.
 6. The process of claim 2 wherein the hydrocarbon fractionin step (c) is a hydrocarbon stream comprising at least 30% by weight ofC11 and C12 n-alkanes and from 15 to 50% by weight of linear C11 and C12mono-olefins.
 7. The process of claim 2 wherein the hydrocarbon fractionin step (c) is a hydrocarbon stream comprising at least 30% by weight ofC13 and C14 n-alkanes and from 10 to 45% by weight of linear C13 and C14mono-olefins.
 8. The process of claim 1 wherein the hydrogen to carbonmonoxide molar ratio in step (c) is in the range of from 1.0 to 5.0. 9.The process of claim 2 wherein the hydrogen to carbon monoxide molarratio in step (c) is in the range of from 1.0 to 5.0.
 10. The process ofclaim 3 wherein the hydrogen to carbon monoxide molar ratio in step (c)is in the range of from 1.0 to 5.0.
 11. The process of claim 4 whereinthe hydrogen to carbon monoxide molar ratio in step (c) is in the rangeof from 1.0 to 5.0.
 12. The process of claim 5 wherein the hydrogen tocarbon monoxide molar ratio in step (c) is in the range of from 1.0 to5.0.
 13. The process of claim 6 wherein the hydrogen to carbon monoxidemolar ratio in step (c) is in the range of from 1.0 to 5.0.
 14. Theprocess of claim 7 wherein the hydrogen to carbon monoxide molar ratioin step (c) is in the range of from 1.0 to 5.0.
 15. The process of claim1 wherein the hydroformylation catalyst used in step (c) is based on asource of cobalt and a substituted or unsubstitutedmonophosphabicycloalkane ligand.
 16. The process of claim 1 wherein step(d) comprises the steps of a first distillative treatment,saponification, water washing treatment and a second distillativetreatment.
 17. The process of claim 16 wherein step (d) additionallycomprises a hydrofinishing treatment.
 18. The process of claim 2 whereinstep (d) comprises the steps of a first distillative treatment,saponification, water washing treatment and a second distillativetreatment.
 19. The process of claim 18 wherein step (d) additionallycomprises a hydrofinishing treatment.
 20. An alcohol compositioncomprising (a) 70 to 90% by weight of C12 and C13 linear primarymono-alcohols and (b) 10 to 30% by weight of C12 and C13 iso-alcoholswherein the weight ratio C12 linear primary alcohol to C13 linearprimary alcohol is in the range of from 0.5 to 2.0.
 21. An alcoholcomposition comprising (a) 55 to 80% by weight of C14 and C15 linearprimary mono-alcohols and (b) 20 to 45% by weight of C14 and C15iso-alcohols wherein the weight ratio C14 linear primary alcohol to C15linear primary alcohol is in the range of from 1.0 to 3.0.